1. Field of the Invention
The present invention is directed to a thrust plate assembly with automatic wear adjustment and a device for securing the automatic wear adjustment against rotation.
2. Description of the Related Art
A prior art friction clutch is disclosed in DE-PS 195 06 698 C2 includes an adjusting device comprising two adjusting rings arranged between an outer diameter area of a diaphragm spring and a pressure plate. A play sensor is located in an axial bore hole in the pressure plate, where it is held by a frictional clamping fit. An actuator portion is connected to the play sensor and has radial inner end located between the outer diameter area of a diaphragm spring and the pressure plate, as viewed in the axial direction, and extends up to a cutout in one of the two adjusting rings. A spring which loads the two adjusting rings in the circumferential direction and axially lengthens the adjusting device additionally reinforces the clamping fit of the play sensor. As wear occurs in the friction linings during operation, this frictional clamping is canceled as a result of the loading by the diaphragm spring, so that an axial distance corresponding to the wear at the friction faces is adjusted between the radial inner end of the actuation portion and the adjusting ring in the region of the cutout. During the next clutch release process, the adjusting device is sufficiently lengthened so that this distance of wear is eliminated. While rotation of the adjusting ring is substantially prevented by the play sensor which reaches into the cutout, torsional vibrations may nevertheless be transmitted to this adjusting ring. It is especially possible for vibrations to transmitted to the adjusting ring when the adjusting ring on the diaphragm spring side is rotated to the extent that one of the walls of the cutout encounters the actuation device of the play sensor. Due to the rotation, but also because of vibrations and torsional vibrations, the clamping of the play sensor in the pressure plate may loosen, so that information about wear for the wear adjusting device may be lost. Particularly in case of strong torsional vibrations, the adjusting ring on the flywheel side may rotate relative to the adjusting ring on the diaphragm spring side, resulting in an arbitrary adjustment of the wear adjustment means.
A prior art thrust plate assembly shown in DE-PS 198 16 519.6-12 has a device which merely prevents reversal of the automatic play compensation adjustment. Accordingly, this prior art cannot prevent the above-mentioned arbitrary adjustment of the wear adjusting means.